Excerpt from International Business Times India (emphasis added )﻿﻿"From the trivalent vaccine the virus is going to get excreted, it is going to get into the environment. In western countries it may not persist in the environment for more than a few weeks but in tropical countries, in environments that are very conducive to polio transmission we expect that it might last for six to 12 months," SG Kasi, a former member of the Indian Academy of Pediatrics, was quoted by scroll.in as saying."When the vaccine is given through the mouth, the liquid that gets dissolved and passed on in the form of stool accumulates in the sewage system. The virus in that vaccine becomes a stronger and more resistant strain," Rajesh Singh, regional health officer, Allahabad was quoted by BBC as saying.